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In 1989, 18-year-old dominatrix Renee Chignell tied cricket umpire Peter Plumley Walker up in her home B&D (Bondage and Domination) dungeon, and left to have a cigarette and coffee. When she returned, something had gone horribly wrong. Walker wasn't breathing.

Later, his body was discovered in Taupo after a panicked Chignell and her boyfriend Neville Walker drove for five hours in the night and threw it into the Huka Falls. Both were later arrested and stood trial – three separate times – for murder.

Now, Chignell's side of the story is being explored in a never-before-seen light in Mistress Mercy: The Renee Chignell Story, part of TVNZ's Sunday Theatre series.

In it, 21-year-old actress Manon Blackman plays Chignell – despite not being alive during the sensational trial, which made headlines in ways New Zealand had never seen before.

"I'd heard of the Huka Falls murder – which, it turns out, isn't actually what happened – but I didn't really know anything," says Blackman, who was born in the UK. "It's actually been amazing realising how many people are so aware of this case, and just how massive it was in New Zealand at the time."

Blackman (who has starred in 800 Words, Terry Teo and Nothing Trivial) stepped right out of her comfort zone to play Chignell, easily her most daring role to date. Along with director Mike Smith, she underwent an intensive research process that involved stepping into the B&D world.

"We went to a B&D establishment, and we spoke to two sex workers about the industry, about the case, about the things I was going to be doing," she says. "I wasn't nervous; yes, it was a whole new world, but I was just super interested and it was a part of the research process."

Manon Blackman: 'It's about really trying to get a grasp of all the circumstances that were affecting Renee at the time'. Photo / supplied

Blackman says it helped her understand the social stigmas that still surround sex work and how those assumptions affected the public's understanding of the case at the time. "Going and talking to these women, it did help to normalise it," she says. "I think with any stigma, there are all of these assumptions that people have . . . and I think that happened a lot with this case.

"Still, today when I mention it, people come out with their version of events and it's like, 'no, that didn't happen'. I think a lot of the stigmas that we have are very unjustified, or based on falsehoods . . . (and) that stigma and that line of work was obviously part of what sensationalised the trial so much."

Blackman never met the real Chignell – but the production crew of Mistress Mercy conducted an interview with her, which is interspersed throughout the film, to gain a proper understanding of her story. Blackman partially drew on this interview for her performance, but says her focus was more on understanding the emotional terror Chignell would have been experiencing at the time.

"That evening . . . I can't even imagine how scary it must have been, and she didn't know what to do. That trauma of finding a dead body and then the panic of not knowing what to do, and being told what to do by Neville, it's very easy to see how that would have been extraordinarily scary."

Sidebar:Also playing in TVNZ's Sunday Theatre season:• In A Flash - The story of the Elim College tragedy in the Mangatepopo Gorge in 2008 (Available On Demand).• Kiwi - The story of the racehorse Kiwi, who won the 1983 Melbourne Cup (Available On Demand).• In Dark Places - The story of Teina Pora's wrongful conviction (Sunday July 22).